Alarm systems for installation in homes, businesses, or in movable vehicles such as automobiles are well known. These systems typically include an alarm controller that is coupled to an alarm annunciator and sensors located throughout the property or vehicle for detecting specific events indicative of a security violation. The alarm controller typically includes a microprocessor or microcontroller with sufficient memory and input/output (I/O) interface devices to effectively couple the controller to the sensors. Home or business alarm systems are typically powered from the standard household current, whereas vehicular alarm systems are typically powered from the battery source of the vehicle. Sometimes a backup battery is included for the alarm controller so the controller remains powered in the event an intruder cuts the power or battery cable.
A variety of sensors are used in such alarm systems. For example, the use of shock sensors in a vehicle to detect a potentially hostile shock, impact, or vibration to the vehicle are well known. See, for example, U.S. Pat. Nos. 6,317,034; 6,140,914; and 5,886,622. In addition to shock sensors, it is well known that motion detectors can be used in a vehicle to detect movement in a radiated field about the vehicle, or to detect the presence of an intruder in a home or business. Finally, vehicular radar detectors employ an alarm system whereby a driver is alerted to the possibility of his or her vehicle being radiated by a law enforcement personnel's radar gun.
One problem with these previously known systems is the susceptibility to false alarms. Vehicles are often parked in areas such as parking garages, shopping mall parking lots, or near heavily traveled roads, or railroad tracks, where they are susceptible to non-hostile vibrations and/or incidental or nonintrusive bumping or contact. In addition, various weather conditions can also cause nonintrusive and harmless contact or vibrations to a vehicle. For example, thunder, hail, or even heavy rain can, at times, trigger a false alarm on a vehicular, home, or business security system.
Similarly, motion detectors used in vehicles, homes, or businesses are susceptible to false alarms. For example, in a high-traffic area, a vehicle's motion detector may be falsely triggered simply by individuals opening a car door next to the alarmed vehicle or by individuals simply closely walking thereby. Similarly, in a home or business context, pets, internal air handling systems blowing papers, or external wind blowing branches next to windows can also trigger false alarms. In addition, in the context of vehicular radar detectors, various radiated energy can create a false indication of the presence of law enforcement radar where none exists.
False alarms from any of these systems are undesirable for a number of reasons. First, in the context of vehicular alarm systems, they tend to drain the vehicle's battery, thus impairing the alarm system's operation for when a valid alarm is warranted. This draining of a vehicle's battery can also impair the vehicle's ability to start when its driver returns. In addition, in vehicle, home, and business systems, frequent false alarms may be ignored by security personnel or bystanders. Moreover, when law enforcement personnel are dispatched in response to an alarm, an individual may be subject to a charge or fee for repetitive false alarms.
In an effort to remedy the false alarm problem, alarm systems have been developed that permit a user to adjust the sensitivity of the alarm for different situations. For example, an alarm system may be put in a test mode and then adjusted to the point of the desired input which will trigger or not trigger the alarm. In a vehicular alarm system, this is typically done by striking the vehicle with a force that is used by the alarm controller as the determinative alarm threshold. In a home or business context, a test may be done while a pet is present to adjust the alarm threshold to a point which a pet would not affect a motion sensor. While these methods give a user some control over the sensitivity of the alarm threshold setting, it does not provide for the situation where the detected input is of the magnitude exceeding the alarm threshold, but the input is still of the nature of an innocent and repetitive occurrence, e.g., the vibrations caused by a thunderstorm. What is needed is an alarm system that provides both the annunciation of an alarm in response to a hostile sensed event, while at the same time the ability to ignore non-hostile but repetitive and anomalous sensed events.